24 THE CACTACEAE. 



where it grows on dry calcareous rocks, and one obtained by Paul Bartsch at Tomaseau in 

 April 1917. Dr. Bartsch states that the flower reminds one very much of a rose and the 

 fruit is pendent like a green plum. 



Lunan in 1814 (Hort. Jam. 2: 236) described a tree nearly a foot in diameter, growing 

 at a residence near Spanish Town, Jamaica, stating that it differed from Pereskia by the 

 absence of tufts of leaves on its fruit. His description points to Pereskia portnlacifolia, 

 but nothing is known of the species in Jamaica at the present day; according to Grisebach, 

 Macfadyen recorded it as cultivated there. 



Illustration: Plumier, PI. Amer. ed. Burmann pi. 197, f. i. 



Figure 20 is copied from the illustration above cited. 



19. Pereskia conzattii sp. nov. 



Tree, 8 to 10 meters high; bark of stems and branches brown and smooth; leaves orbicular to 

 obovate, acute, i to 2.5 cm. long; areoles small, with short white wool and a few long hairs; spines 2 

 to 6 on young branches, 10 to 20 on main stem, acicular, 2 to 2.5 cm. long, at first yellowish brown, 

 dark brown in age; flowers not known; ovary bearing small scales; fruit naked, pear-shaped, more 

 or less stalked at base, 3 to 4 cm. long; seeds black, glossy, 3 mm. long, with a small white hilum. 



Collected at Salina Cruz and Tehuantepec, Oaxaca, Mexico, in February and April, 

 1913, by Professor C. Conzatti; probably also in Guatemala. 



SPECIES UNKNOWN TO Us. 



Pcrcsl'in nffiiii'i ;ind /'. haageana Meinshausen, Wochenschr. G;irtn. Pflanz. 2: 118. 1859. 



Pereskia cruoita, P. grandifiora, and P.(?) plantaginea, the first two given as synonyms 

 and the last merely mentioned by Pfeiffer (Enum. Cact. pp. 176, 177, and 179) can not be 

 identified. The same is true of P. grandispina Forbes (Journ. Hort. Tour Germ. 159. 1837). 



Tribe 2. OPUNTIEAE. 



Plants usually very fleshy, never epiphytic, branched (usually much branched), one to many- 

 jointed; joints diverse in structure, terete, compressed, or much flattened, with irregularly scattered 

 areoles, ribless, except one species; leaves usually caducous, but in some species more or less persist- 

 ent, small or minute, subulate or cylindric, in one genus broad and flat; areoles usually glochidif- 

 erous (except in Maihuenia; in Grusonia only those of the ovary), mostly spine-bearing; spines 

 usually slender, straight or nearly so, sometimes sheathed ; corolla mostly rotate (sepals and petals 

 in .Yo/>i//r<; erect) ; flowers sessile, diurnal, one from an areole; fruit usually a fleshy berry, sometimes 

 dry, rarely capsular; seed white or black, globular, flattened or even winged, with a thin or hard 

 testa; cotyledons large, elongated. 



This tribe contains 7 genera and at least 300 species, various in habit, flower, fruit, 

 and seeds. It is more closely related to the Pcrcskieae than to the Ccrccac. The following 

 characters possessed by some or all genera of the Opiinticae are wanting in the Ccrccac: 



Leaves on the stem (see also Harrisia and Hylocercus) ; glochids in the areoles; sensi- 

 tive stamens; sheathed spines; winged, white, and bony-covered seeds; the separation of 

 withering calyx, stamens, and style from the ovary; areoles irregularly distributed over the 

 stem in all the genera except (irnsoiiia, in which they are arranged on ribs as in many of 

 the Ccrccae. 



The tribe is distributed throughout the cactus regions of the Americas, but the genera, 

 except Opuntia, are localized. 



KEY TO GENERA. 



Leaves broad and flat i . Pereskiopsis 



Leaves subulate or cylindric. 



Seeds broadly winged .... ... 2. Pterocactits 



Seeds wingless. 



Stamens much longer than the petals. 



Petals erect; joints flat .3. Nnpalea 



Petals recurved; joints terete . . . 4. Tiifinyi 



Stamens shorter than the petals. 

 Joints flat to terete, not ribbed. 



Testa of the seed thin, black, shining . 5. Maihuenia 

 Testa thick, pale, dull . 6. Opuntia 

 Joints terete, longitudinally ribbed 7. Grusonia 



